MPs have voted overwhelmingly in favour of plans to ban smoking in cars carrying children by 376 votes to 107, a majority of 269.
Shadow public health minister Luciana Berger has said those opposed to a ban on smoking in cars carrying children are the same people who railed against the introduction of laws enforcing seatbelt use throughout the 1970s and 1980s.
The Labour MP, who is urging her Commons colleagues to vote in favour of the ban, said health figures suggest around half a million children are exposed to second hand smoke in the back of the car on a weekly basis.
Critics of the anti-smoking legislation, though, have said such a ban cannot be implemented or will be ineffective - a similar argument, Ms Berger said, that was used to oppose seatbelt laws.
She admitted that "we don't have the exact specifics about how it will work in practice", but said MPs will look to "states in the US," plus "Canada, Australia and South Africa", to see how their equivalent laws are targeting offenders.
MPs have been tweeting their intentions ahead of today's vote in the House of Commons on a legal ban on people smoking in cars carrying children.
I will be voting later today for smoking ban in cars to protect children
My libertarian instincts are wrestling with my profound belief that public health is one of biggest issues facing population #smokingban
Support a ban on smoking in cars and other vehicles - to protect the health of children and others.
The Commons is expected to vote in favour of the ban, though Prime Minister David Cameron - who has declined to share his view on the issue - is set to miss the vote as he remains involved in the Government's response to the floods crisis in the South West of England.
Boris Johnson has used his column in the Daily Telegraph to appeal to party colleagues to accept the "bossyboots brigade" he so often rails against are right in the case of a smoking ban in cars where children are present.
"Surely to goodness - you might say - people these days are aware of the problem of passive smoking? Surely all smokers know that they shouldn't be puffing away in a car, while the pink defenceless lungs of kids are sucking in the evil vapours?" he wrote.
"Alas, I am afraid that people either don't know, or don't care enough.""These kids cannot protest, and very often the smoker in the vehicle lacks the will to stub it out. "This law would give that smoker that extra legal imperative to obey their conscience and do the right thing."
Rejecting critics' claims that it would divert police resources from more serious crimes, he said it would be "largely enforced by the natural social pressure of disapproval backed by law".
The chair of the Royal College of Physicians' tobacco advisory group, John Britton, says the RCP is calling on MPs to support "this important health amendment".
The evidence shows the importance of protecting children from passive smoking, and cars are still a major area of exposure.
Such exposure is widely associated with adverse health effects, including an increased risk of respiratory and allergic symptoms. That is why the RCP is calling on MPs to support this important public health amendment.
But pro-smoking groups have said the restriction would be an "unnecessary intrusion into people's private lives.
MPs will vote today on whether or not people should be prohibited from smoking in cars with children present as the Children and Families Bill returns to the Commons.
The Bill was amended in the House of Lords after Labour tabled an amendment which would give the Health Secretary the power to make it illegal to smoke in a car carrying children. Peers have now accepted a Government-backed version of the amendment.
Every year 160,000 children are adversely affected by second-hand smoking, costing the NHS in England more than £23 million, the Royal College of Physicians (RCP) said.
On Thursday, 692 doctors, nurses and other health professionals and experts had signed up to support the ban on smoking in cars.Their letter in the British Medical Journal (BMJ) said:
Secondhand exposure to tobacco smoke is a major cause of ill health in children.
Smoke inhalation damages the developing lung, and the Royal College of Physicians estimates that each year in the UK it is responsible for 300,000 primary care contacts, 9,500 hospital admissions, at least 200 cases of bacterial meningitis and 40 sudden infant deaths.
Most of this additional burden of disease falls on the more disadvantaged children in society, and all of it is avoidable.
Around 700 health experts and medics have called upon on the Government to ban smoking in cars carrying children ahead of a Commons vote on Monday.
In a letter to the British Medical Journal (BMJ), respiratory experts said secondhand smoke was a "major cause of ill health in children", damaging the developing lungs, causing sudden infant death and leading to thousands of hospital trips every year.
Signatories to the letter are being coordinated by Dr Nicholas Hopkinson from Imperial College London and chairman of the British Thoracic Society's chronic obstructive pulmonary disease specialist advisory group.
Lib Dem leader Nick Clegg has suggested a proposal to ban smoking in cars carrying children would be comparable to trying to legislate to stop a child watching too much TV or drinking too many fizzy drinks.
The Deputy Prime Minister made it clear he would not back such a ban after the Labour plan was approved last night by the House of Lords.
Speaking on LBC radio, Mr Clegg said: "Of course it is a stupid thing to do to smoke in a car with kids in the back, of course it is - in the same way you shouldn't give your children a can of Coke before going to bed or only feed them on crisps breakfast, lunch and supper.
"I think you shouldn't legislate unless you think it is going to make a difference, and I don't see how this is going to be enforced. "
Smoking in cars carrying children could be banned after peers defeated the Government on the issue by 222 votes to 197.